Method of producing a carbonaceous product from low grade coal



March 1962 w. MUSCHENBORN ETAL 3,02

METHOD OF PRODUCING A CARBONACEOUS PRODUCT FROM LOW GRADE COAL FiledMarch 14, 1957 FEED HOPPER PICKING BELT 3 DRYING APPARATUS HEAT TREATINGAPPARATUS DEWATERING SCREEN INVENTOR WALTER MUSCHENBORN ERICH NGTZOLD BYW ATTORNEY United States Patent 3,026,252 METHOD OF PRODUCING ACARBONACEOUS PRODUCT FROM LOW GRADE COAL Walter Miischenhorn, 39Elfriedestrasse, Essen, Germany,

and Erich Notzold, 29 Ehrenaue, Essen-Haarzopf, Germany Filed Mar. 14,1957, Ser. No. 645,881 Claims priority, application Germany Mar. 20,1956 7 Claims. (Cl. 202-31) The invention relates to a method ofdressing coalcontaining materials, more particularly materialscontaining a high percentage of ash or comprising coal which isintimately combined with unwanted substances.

The main object of the invention is to enable the chicient refining oflow-grade coal-containing materials; these materials occur in extremelylarge quantities, notably as the geologically more recent coals rich ingas, for example lignite and brown coal in general.

The coal-containing materials with which the invention is concerned havea comparatively low specific weight, due to their low total percentageof mineral substance as compared with the volatile components and thebound water content. For example a ligneous brown coal may contain 15%pure rock material (with 80% residue on ignition), 20% bound water, 40%volatile hydrocarbons and a mere 25% of solid carbonaceous substance,and may despite its comparatively high ash content have a specificweight of only about 1.3. Moreover the particles of coal are intimatelycombined in the whole with the ash-containing material, there beinghardly any free rock materiaL' Owing to the slight differences betweenthe specific weights of the coal proper and the ash-containing materialin a coal of this nature, the coal cannot be dressed by a normal washingprocess, for example in a settling tank, by trough washing, hearthwashing or by heavy liquid treatment, despite the frequentlyconsiderable differences in the ash content of the individual'pieces orgrains or can be dressed at the most with an uneconomically low yield.

Furthermore the known fine-grain dressing processes, in particular thefroth flotation or converter process, cannot be employed owing partly tothe high cost of the fine disintegration required and partly to theunsatisfactory separation achieved by these processes; this latterdisadvantage is consequence of the intimate combination of the coalproper with the ash-containing material, and the low specific weight.

For these reasons, the only economic way to use these coals, assumingthat it was considered worth while to mine them in the first place, hasheretofore been simply to burn them, for example in boilerhouses; evenso they have been unsatisfactory owing to the high percentage of ash.

The invention provides a new method by which such coal-containingmaterials can be economically dressed. In accordance with the inventionthe raw coal or the like is subjected, either directly or afterseparation of the coarse impurities and preliminary disintergration asby crushing to a suitable granular size, to a coking operation by meansof which the volatile constituents (which are recovered as such) and thewate are expelled wholly or in part, whereupon the coked product isseparated by one of the usual dressing processes into its componentswhich are respectively poor in ash and rich in ash.

The coking operation is carried out at temperatures which are selectedwith regard to the granular size or granular condition of the coke to beproduced: these temperatures may range between a temperature appropriateto a low-temperature coking or carbonising process and thosetemperatures which are usual in the production 3,026,252 Patented Mar.20, 1952 of high-temperature coke. It is recognized in the industry thatlow temperature coking is carried on at a temperature of the order of650 C. and high temperature coking is carried on at a temperature of theorder of 1100" C.

The success of the new method is due to the expulsion from the coal,during the coking operation, of the bound water and volatilehydrocarbons and also changes in the mineral substances (carbonates,sulphides, etc.) in consequence of the action of heat; as a result thedifference in the specific weights of the components of the cokedproduct is much greater than the corresponding difference before coking.

The conversion of the coal proper into coke theoretically increases itsspecific weight but, particularly with raw materials having a highpercentage of volatile constituents (with which the invention isprimarily concerned), the coal particles become very porous; theirapparent specific weight therefore becomes quite low.

As mentioned above the coking operation also effects a change in theash-containing mineral substances; before the coking operation thesesubstances have only a slightly greater specific weight than the coalproper but after coking they become, in eifect, much heavier. This isdue to chemical conversion on heating since the ashcontaining mineralsubstances yield only very little water and gaseous matter.

The resulting difierentiation in the specific weights of the componentshaving the low and the high proportion of ash, enables them to beseparated by a normal dressing treatment, e.g. the usual equal settlingmethod or, particularly advantageously owing to greater discrimination,a heavy liquid treatment.

In the latter case it is desirable, before introduction of the materialto be dressed into the separating liquid, to render the surface of theparticles water-repellent, for example by a spray treatment with oil,and thus to prevent penetration of the heavy liquid into the pores ofthe particles. The oil used to render the surface of the particleswater-repellant can be an oil of high viscosity such as a petroleumdistillate having a viscosity of S.U.S. at 210 F.

The diiferentiation in the specific Weights of the coal andash-containing substances which is obtained in the coking operation alsoresults in considerable moderation in the final ash content when themethod of the invention is applied to pro-Washed coal; i.e. the same iscoked and then again separated.

If the material resulting from the coking operation is lumpy thematerial is either separated directly after that operation or is firstreduced by crushing to the granular size which is most favourable asregards the dressing process to be employed.

Generally speaking, however, the coking operation itself causes thematerial to break up into smaller pieces, which then merely requirescreening for separation of the finest grains.

As an example of the possibilities inherent in the new method it may bementioned that on its application to raw coal having the composition setforth above and subsequent reduction in size of the coke produced toless than 10 mm. granular size, there was obtained by heavy liquidtreatment at a specific separating weight of 1.35, from a granular sizeof 10 to 0.5 mm., a coke concentrate having 11% ash, with a yield of60%. Heavy liquid treatment is well known in the art and can be forexample tetrachlorocarbone. In any case it is a medium of higher densitythan water, and usually such medium is obtained by admixing to water afine powdered heavy material, such for example as magnetite.

Apart from the main advantages of the new method there is also a furtheradvantage in the avoidance of an exacting operation to reduce theparticle size of the raw coal prior to the dressing operation, as therequisite particle size reduction occurs either automatically on cokingor can be performed easily on the very porous coke.

This advantage also makes the new process very suitable for the refiningof raw coal in general, i.e., not only coal the nature of which rendersits preparation subject to the difficulties referred to above.

The coke concentrate which is obtained as the final product of themethod according to the invention, may either be used without furtherprocmsing or may form the basic material for a further refining to formblock coke, the coke concentrate being briquetted together with bindingagents and coked again.

Reference to the schematic drawing will more clearly reveal the steps ofthe invention. In the drawing 1 is a feeding hopper; 2 is a pickingbelt; 3 is a drying apparatus; 4 is a heat treating apparatus, i.e., afurnace; 5 is a heavy liquid separation device; 6 is a dewateringscreen; and 7 is a hopper.

An example of the method of this invention is as follows. A rawcoal-containing material having a high content of volatile matter andwater was fed into hopper 1. The material was a Southern German lignitewhich consist'ed of alternating strips having varying volatile matterand ash contents. The average ash content was about 12%, the averagevolatile matter content was about 42%, and the average water content wasabout 35%. The total solids-content was about 23% of which about 18% wasclean coal. This coal-containing material could not be economicallycleaned at all according to conventional separating processes. Thematerial was fed from hopper 1 to the picking belt 2 and the rock piecesof bigger size were removed. The material was passed into the dryingapparatus 3 and dried by heating to a temperature of about 120 C. Thedried material was then passed into the furnace 4 and heated to about600 C. As a result of the heat treatment, the material disintegratedinto granular particles of relatively small grain size. The particlesnow being of different apparent specific gravities due to the previoustreatment were subjected to a heavy liquid separation in the separationdevice 5. The device contained tetrachlorcarbone as the heavy liquidmedium. The particles were separated therein into a rich cokeconcentrate having a relatively low ash content and a waste portion highin ash content. The waste ash portion was discarded. The cokeconcentrate (product) was dewatered on the dewatering screen 6 and fedinto hopper 7.

We claim:

1. A method for producing a carbonaceous product of low ash content fromlow grade coal-containing material having a high ash content and a highproportion of volatile matter comprising disintegrating said material 4by coking, and subjecting said disintegrated material to a wetseparation process to obtain a carbonaceous concentrate relatively lowin ash content and a separated ashrich component.

2. The method of claim 1 wherein said low grade coalcontaining materialis subjected to a crushing treatment prior to said coking step.

3. The method of claim 1 wherein said wet separation process is a heavyliquid separation process which involves the use of a heavy liquid.

4. A method of producing a carbonaceous product of low ash content fromlow grade coal-containing material having a high ash content and a highproportion of volatile matter comprising disintegrating said material bycoking to produce a disintegrated, porous, coked material, treating saidporous material with a water-repellant agent to thereby minimizewater-penetration into the pores thereof, and subjecting saidwater-repellant material to a heavy-liquid separation operation whichinvolves the use of a heavy liquid to obtain a carbonaceous concentraterelatively low in ash content and a separated ash-rich component.

5. The method of claim 4 wherein said porous coked material is crushedprior to the treatment thereof with the water-repellant agent.

6. The method of claim 4 wherein said water-repellant agent is oil andthe oil is sprayed onto said porous coked material.

7. A method of producing a carbonaceous product of low ash content fromlow grade coal-containing material having a high ash content, a highproportion of volatile matter and coarse impurities comprising crushingsaid material and separating coarse impurities, disintegrating saidcrushed material by coking to produce a porous disintegrated coke,rendering said porous coked material water-repellant, and subjectingsaid water-repellant material to a heavy liquid separation operationwhich involves the use of a heavy liquid to obtain a coke concentraterelatively low in ash content and a separated ash-rich component.

References Cited in the file of this patent UNITED STATES PATENTS1,334,170 Runge Mar. 16, 1920 1,466,377 Jung Aug. 28, 1923 1,995,603Cunningham Mar. 26, 1935 2,636,688 Singh Apr. 28, 1953 2,803,587 JungAug. 20, 1957 FOREIGN PATENTS 240,799 Great Britain July 8, 192.6

1. A METHOD FOR PRODUCING A CARABONACEOUS PRODUCT OF LOW ASH CONTENT FROLOW GRADE COAL-CONTAINING MATERIAL HAVING A HIGH ASH CONTENT AND A HIGHPROPORTION OF VOLATILE MATTER COMPRISING DISINTEGRATING SAID MATERIAL BYCOKING, AND SUBJECTING SAID DISINTEGRATED MATERIAL TO A WET SEPARATAIONPROCESS TO OBTAIN A CARBONACEOUS CONCENTRATAE RELATIVELY LOW IN ASHCONTENT AND A SEPARATED ASHRICH COMPONENT.